Temperature is an extremely important element to orchid growing. Temperature ranges are customarily categorized as warm-growing, intermediate and cool-growing. Here are the quick and dirty guidelines:
| Day Ranges | Night Range | Sample Orchids Enjoying This Range | |
|---|---|---|---|
| Warm | 70–85°F (21-29°C) |
65–70°F (18-21°C) |
Phalaenopsis (moth orchid) |
| Intermediate | 65–75°F (18-24°C) |
55–65°F (13-18°C) |
Cattleya (corsage orchid), Miltonia |
| Cool | 60–70°F (15-21°C) |
50–55°F (10-13°C) |
Masdavallia, Odotonglossum |
These are not absolute rules. You may find that some intermediate orchids will do perfectly fine several degrees warmer or colder, whereas others might prefer a narrower range.
Plant Origins
Depending on their origins, different orchids prefer different temperatures. Generally speaking, the higher their natural habitat, the cooler they like. For example, Miltonia orchids come from the mid altitude of Brazil, so they prefer a night temperature in the low 50°F (10°C) in the winter night and high 70°F (26°C) in the summer day. Whereas most Phalaenopsis orchids come from near the sea level, so they like their night temperature in the mid 60°F (16°C and 20°C).
Day and Night
Although many orchids have a fairly wide range of tolerance to day temperature, the night ranges are crucial. Most orchids require at least 10°F to 15°F (12°C and 9°C) cooler at night to initiate flower spikes. In some place, the day/night variation is even bigger in certain seasons. For example, an intermediate kind might refuse to flower unless the ambience drops to 55°F (13°C ) for two months or more. That’s why orchids always grows poorly in an enclosed office environment with constant temperature (in additions to the fact that there isn’t enough light). If you grow your plant close to the window or outside, the natural variation should already take care of this requirement for you.
Minor Adjustments
Unless you have a greenhouse with sophisticated thermal control, it is difficult to grow an orchid that does not like your home natural condition. If you live in Florida, for example, it’s hard to make a cool-growing Odontoglossum happy. Buying and growing orchids that suit your environment will make your life easier. However, if you have an occasional cold spell, you can put your orchids on a heat mat to ensure they don’t freeze too much. But touch your mat to make sure it’s not cooking your plants. Likewise, I found that putting an orchid in a clay pot (along with its original pot) can keep the orchid a bit cooler. You can also turn on a fan to cool down the place. These tricks will widen your ranges a little. If your orchid is not doing well or will not flower at its current location, move it to another window might improve the condition.
Happy growing!